Mill with rotating air stream

ABSTRACT

A mill comprising a casing and a drumlike stator mounted axially within the casing and in spaced relationship to the wall thereof. The stator is open at the end adjacent the mill inlet and closed at the end adjacent the mill outlet. An inlet to the casing is provided through which air may be introduced into the interior of the stator. A plurality of vanes is associated with the peripheral wall of the stator and extends lengthwise thereof. Slots are provided between the vanes through which air emerges from the stator with a rotational movement imparted by the vanes. An inlet to the casing is provided through which material to be processed may be introduced into the annular space between the wall of the casing and the peripheral wall of the stator there to be contacted by the rotating air stream. An axial outlet from the casing is provided at the opposite end to the air inlet. A drive shaft extends axially into the casing with a vaned classifier rotor mounted on the inner end of the drive shaft between the stator and the outlet. The rotating airstream causes the material particles to rub against one another and also to be impacted against the interior of the casing.

United States Patent Ronald Frederick Bourne Transvaal. Republic ofSouth Africa [72] Inventor [54] MILL WITH ROTATING AIR STREAM 2 Claims,4 Drawing Figs.

[52] US. Cl 241/39 [51] Int. Cl 1302c 19/06 [50] Field ofSearch 241/5,39,

[56] References Cited UNITED STATES PATENTS 2,092,307 9/1937 Gaffney24l/S6X 2,981,489 4/1961 Hannum 241/275 3,423,034 1/1969 Hippert 241/55Primary Examiner-Donald 0. Kelly An0rneyYoung & Thompson ABSTRACT: Amill comprising a casing and a drumlikc stator mounted axially withinthe casing and in spaced relationship to the wall thereof. The stator isopen at the end adjacent the mill inlet and closed at the end adjacentthe mill outlet. An inlet to the casing is provided through which airmay be introduced into the interior of the stator. A plurality of vanesis associated with the peripheral wall of the stator and extendslengthwise thereof. Slots are provided between the vanes through whichair emerges from the stator with a rotational movement imparted by thevanes. An inlet to the casing is provided through which material to beprocessed may be introduced into the annular space between the wall ofthe casing and the peripheral wall of the stator there to be contactedby the rotating air stream. An axial outlet from the casing is providedat the opposite end to the air inlet. A drive shaft extends axially intothe casing with a vaned classifier rotor mounted on the inner end of thedrive shaft between the stator and the outlet. The rotating airstreamcauses the material particles to rub against one another and also to beimpacted against the interior of the casing.

PATENTEU JAN 5 law sum 2 [IF 2 MILL WITH ROTATING AIR STREAM Thisinvention relates to mills such as are used for reducing particles tofiner fractions. 1

The main object of the invention is to provide a novel type of millwhich will perform the function of grinding, separating and classifyingmaterials.

A mill in accordance with the invention comprises a casing; a drumlikestator mounted axially within the casing and in spaced relationship tothe wall thereof, said stator being open at the end adjacent the millinlet and closed at the end adjacent the mill outlet; an inlet to thecasing through which air may be introduced into the interior of thestator; a plurality of vanes associated with the peripheral wall of thestator and extending lengthwise thereof; slots between the vanes throughwhich air emerges from the stator with a rotational movement imparted bythe vanes; an inlet to the casing through which material to be processedmay be introduced into the annular space between the wall of the casingand the peripheral wall of the stator there to be contacted by therotating airstream; an axial outlet from the casing at the opposite endto the air inlet; a drive shaft extending axially into the casing; avaned classifier rotor mounted on the inner end of the drive shaftbetween the stator and the outlet; and means for inducing a flow of airinto the casing.

The air may be introduced under pressure. Alternatively, atmospheric airmay be drawn into the casing under suction.

Also according to the invention, the air inlet is arranged to impartrotational movement to the air stream before it enters the casing.

The mill of the invention will be further described, purely by way ofexample, with reference to the accompanying drawings, in which:

FIG. 1 is a longitudinal section through a mill according to theinvention;

FIG. 2 is a cross section on the line lI-II of FIG. 1;

FIG. 3 is a cross section on the line III-Ill of FIG. 1, on an enlargedscale; and

FIG. 4 is a diagrammatic view of the mill and ancillary equipment.

Referring to the drawings, the casing 1 is in the form of a cylindricaldrum having an inlet 2 for material to be treated at or near one endthereof. At the same end of the drum there is provided a conelikeaxially disposed inlet 3 for air. The air is introduced tangentiallyinto the cone and it enters .the mill in a rotating stream.

Within the casing l and adjacent the inlet end thereof, a stator 4 ismounted on an axial sleeve 5. The stator is in the form of a drum whichis open at the end adjacent the air inlet 3 and closed at the other end.The periphery of the drum is provided with a plurality of lengthwiseslots 6 extending between lengthwise vanes 7. The incoming airstreamenters the interior of the stator and emerges through the slots at highvelocity. The vanes 7 impart further rotational movement to theairstream.

An axial outlet duct 8 is provided at the opposite end of the casing tothat in which the air inlet is disposed.

A drive shaft 9 extends through the stator-supporting sleeve and itcarries on its inner end a vaned rotor 10 which is disposed between thestator 4 and the outlet duct 8. The rotor comprises a plurality ofblades 11 and concave annular shrouds l2 and 13 supported in spacedrelationship to one another by the blades which extend between them.

Optionally, the lower part of the casing adjacent the rotor is providedwith an outlet 14 for oversize material. The duct 8 is mounted in acylindrical guide sleeve 15 which is carried by arms 16 and it isadjustable axially towards and away from the rotor 10. This adjustmentenables the gap, and therefore any inward leak of atmospheric air,between the duct 8 and rotor 10 to be set at a minimum or as desired.

In one embodiment, air is introduced into the casing by means of apressure fan 17 and is discharged therefrom via a suction fan 18. Thisarrangement will cause the highest velocity. The suction fan maymbedispensed withif desired. ln an alternative arrangement, t e pressurefan is dispensed with and air flow induced by the suction fan alone.

In use, air emerges through the slots in the stator at a predeterminedvelocity. The rotating airstream causes the particles introduced intothe casing to rub against one another and also to be impacted againstthe interior of the casing. This reduces the particles in size and theypass to the rotor zone where the rotor acts as a classifier. The finestogether with air leaves the mill via the outlet duct and the oversizefraction is either retained for further reduction or, in the case wherea separate outlet for oversize particlesis provided, removedtherethrough.

The mill of the invention not only has less wearing parts than theconventional type of impact mill but the effect on the material to betreated may be varied by altering the velocity of the airstream. Thus,in the treatment of asbestos a relatively low air velocity may beemployed and fibre together with sized grit may be withdrawn from themill with minimum damage to the fibre. This sized grit can all beremoved subsequently by a suitable screening operation. On the otherhand, extremely high velocities can be employed for materials for whichthey are especially suitable. 1

Iclaim:

l. A mill comprising a casing; a hollow cylindrical stator mountedaxially within the casing and in spaced relationship thereto, saidstator having a peripheral wall and being open at one end and closed atthe other; an inlet to the casing through which air may be introducedinto the interior of the stator through the open end thereof; aplurality of vanes around the peripheral wall of the stator andextending lengthwise thereof; slots between the vanes through which airemerges from the stator with a rotational movement imparted by thevanes; an inlet to the casing through which material to be processed maybe introduced into the space between the casing and the stator there tobe contacted by the rotating airstream; an axial outlet from the casingat the opposite end to the air inlet; a drive shaft extending axiallyinto the casing; a vaned classifier rotor mounted on the drive shaftbetween the closed end of the stator and the outlet; and means forinducing a flow of air into the casing.

2. The mill of claim 1, in which the air inlet is arranged to impartrotational movement to the airstream before it enters the stator.

1. A mill comprising a casing; a hollow cylindrical stator mountedaxially within the casing and in spaced relationship thereto, saidstator having a peripheral wall and being open at one end and closed atthe other; an inlet to the casing through which air may be introducedinto the interior of the stator through the open end thereof; aplurality of vanes around the peripheral wall of the stator andextending lengthwise thereof; slots between the vanes through which airemerges from the stator with a rotational movement imparted by thevanes; an inlet to the casing through which material to be processed maybe introduced into the space between the casing and the stator there tobe contacted by the rotating airstream; an axial outlet from the casingat the opposite end to the air inlet; a drive shaft extending axiallyinto the casing; a vaned classifier rotor mounted on the drive shaftbetween the closed end of the stator and the outlet; and means forinducing a flow of air into the casing.
 2. The mill of claim 1, in whichthe air inlet is arranged to impart rotational movement to the airstreambefore it enters the stator.